Synthetic fibers having a natural crimp and method for preparing the same



' March 31, 1959 B. H. CARR ETAL SYNTHETIC FIBERS HAVING A NATURAL CRIMP AND METHOD FOR PREPARING THE Filed April 9, 1956 SAME v all :lll

INVEN TORS. fioydh. Carr Ro/andE una erman Rober/ M Aarll'nslrl' X/Z f azZ-V AGENT United St v a efltQ i SYNTHETIC FIBERS HAVINGANATURAL CRIMP AND METHOD FOR PREPARING THE SAME 3 Application April 9,1956, Serial No. 576,775 6 Claims. (Cl. 1s-s4) Thisinvention relates to an improved method for. preparing synthetic fibers. -More particularly it relates to such a method for prcparingsynthetic fibers havingwa naturalcrimp. T= r Useful continuous fibers have been prepared from polymers by the continuous localized'coagulation of latexes of those polymers. Thus, in one case a latex of a suit-- able polymer was spun throughnozzles or spinnerets'into an aqueous coagulant bath and the fibrous coagulum withdrawn continuously at thexrate at which it was spun. The coagulum was washed to remove coagulanhfused to a continuous, coherent fiber, supercooled and oriented by stretching the fiber beyond the limit of elastic recovery. In another case, the converse technique was used of continuously spinningasuitable coagulant into a bath of the polymer latex and withdrawingthe fibrous coagulum continuously therefrom. The coagulum was again washed, fused, supercooled, and oriented. =The fibers produced by that latter technique were hollow and, because of such unique character, were possessed of highly desirable properties. The fibers resulting from both of the above discussed methods had the disadvantage of being smooth and straight. For yarn making operations it was necessary'to impartan artificial crimp to the fibers requiring an added procedural. step. It would therefore be desirable to haveamethod for preparing synthetic fibers which do not require an artificial crimp. Some of the other disadvantagesof prior synthetic fibers made from polymer latexesha've been poor dye receptivity and poor moisture absorption which have somewhat I retarded their acceptance 'in many fields.

It is accordingly the principal object of this invention to provide a method for preparing fibers having a natural crimp. l v

It is a further object to provide such a process based upon the continuous localized coagulation of a latex of a polymer; 1 v t It is a still further object to provide a process for preparing fibers having improved dye receptivity and moisture absorption.

Another object is the provision of a new class ofsynthetic fibers. ,1

The aboveand related objects are accomplished by means of [process whereby a liquid coagulant electrolyte having dissolvedt'herein fiber forming amountsof a I po1ymeric rnaterial is brought into continuous contact y with a latex of a fiber forming normally crystalline poly- "mer and withdrawing continuously the so-formed filamentary coagulum at the same rate as that at which it is formed, washing the continuous filamentary coagulum. to remove residual entrapped electrolytecoagulant, drying at a given temperature. I --teri-al must additionally form a solution capable of toler- 2,880,056 Patented Mar. 31', 1959 and fusing the continuous filamentary coagulum to produce a continuous fiber, supercooling the fiber and stretching the fiber to produce. orientation. The result of this spinning process is a continuous fiber having a natural crimp and consisting of a hollow cylindrical fiber withina dissimilar hollow fiber.

The polymers Whose latexes have been found to be useful are-those normally crystalline polymers capable of forming fibers and capable of localized or instantaneous coagulation from a latex. As a preferred class of such polymers may be mentioned the normally crystalline vinylidene chloride polymers which are composed predominantly of vinylidene chloride and may contain significant but minor amounts of a comonomer such as vinyl chloride, vinyl" acetate, and acrylonitrile. Such polymers are easily prepared in latex, form, are capable of localized coagulation, and form useful fibers.

In a typical preparation of those latexes a monomeric material consisting principally of vinylidene chloride with'minor amounts of a comonomer is dispersed into an aqueous phase containing emulsifying quantities of a surface! active agent and a water soluble polymerization catalyst to form an oil-in-water emulsion. Polymerization is initiated-and maintained by warming the emulsion to a temperature usually of from 40 C. to 70 C. Followingcompletion of polymerization the latex is filtered to remove any precoagulum. If the latex is to be stored for any appreciable length of time it is a common practice to add more'surface active agent to enhance the shelf stability of the latex. i

It is well known that some latexes form useful coherent articles in unplasticized condition while others require a plasticizer. The process of this invention contemplates the use of either unplasticized or plasticized latexes. 'Other common practices prior to the fabrication of articles from latexes are the thickening of the aqueous phase with a hydrophilic colloid, such as methyl cellulose, and the elevation-of the pH of the latex, usually with ammonium-hydroxide. All of the above latexformulation steps may be employed in this process if needed. Likewise the usual additions such as pigments, fillers, dyes, and the like may be blended with the latex prior to spinning.

' Thesecond polymeric material, hereinafter referred to as the dissimilar polymeric material, must be capable of dissolution in the aqueous coagulant either with or without the aid of a water-miscible mutual solvent. The dissimilar polymeric material must be dissimilar to the polymer of the latex, at least to the extent of exhibiting a'diiferent limiting degree of orientation or a difierent elastic limit when formed into filaments and stretched The dissimilar polymeric maating amounts capable of coagulating a latex of an electrolyte coagulant and capable of coprecipitation with the coagulation of the latex. When latexes of the normally crystalline vinylidene chloride polymers are used, an especially useful and a preferred dissimilar polymeric material is zein. Another which may be named is polyvinyl alcohol .or partially hydrolyzed polyvinyl acetate.

The electrolytescapableof coagulating polymer latexes are well known in the art and consist of watersoluble, inorganic salts; It is generally accepted'that the polyvalent metallic salts are more etficient and come quently more useful coagulants. Specific mention may be known made of calcium chloride, magnesium chloride, aluminum sulfate, and barium chloride.

The aqueous coagulant consists of the two solutes, electrolyte coagulant and dissimilar polymeric material, in a mutual solvent for both. The concentrations of each of the solutes will depend upon the concentration of electrolyte required to coagulate the latex, upon the concentration of dissimilar polymeric material required to produce continuous coherent fibers and upon the solubility tolerance of each of the materials for each other in the mutual solvent. For reasons of cost, safety, and ease of handling it is preferred to employ as much water in the solvent as possible. Water is a non-solvent for the latex polymers employed and is an excellent solvent for the electrolyte coagulants. When water is a solvent for the dissimilar polymeric material, there is no need for an additional mutual solvent, and water may be used alone. However, most of the dissimilar polymeric materials are soluble in water to only a limited extent or are diflicult to dissolve, so that a water-miscible mutual organic solvent may be employed. Typical of such solvents are the lower water miscible alcohols and acetone. Since such solvents must be removed following the fiber formation it is desirable that the mutual solvent be at least as volatile as water so that the water and solvent may be eliminated from the fiber with one drying step.

The electrolyte should be used in a solution of 3 to percent by weight concentration. When less than 3 percent is employed the required instantaneous coagulation of the latex is not always achieved. When more than 10 percent is used no beneficial result is obtained and extra washing steps are needed to remove the coagulant. The actual amount used will be determined by the coagulating efiiciency of the coagulant and the electrolyte stability of the latex. Trivalent metal salts are usually more efficient coagulants than bivalent although some trivalent salts may have limited water solubility in which case a water soluble bivalent salt would be more efficient. The stability of the latex to electrolytes will vary depending on the emulsifier system used in its preparation. An investigator will be able to determine the tolerance of any given latex to any given electrolyte by a simple preliminary experiment.

The dissimilar polymeric material must be employed in an amount sulficient to prepare a continuous filamentary core in the fiber. With the natural materials such as zein, it has been found that the coagulant must contain at least 10 percent by weight of the dissimilar polymeric material, and that it is preferred to have at least percent zein present in the aqueous coagulant solution.

In the drawing,

Fig. 1 represents a schematic embodiment of a manner of carrying out the steps of the process.

Fig. 2 represents a cross section of the filamentary article taken across line 22 of Fig. 1, and

Fig. 3 represents a cross section of the filamentary article taken across line 3-3 of Fig. 1.

In a typical preparation, the aqueous coagulant solution is fed from an inventory of solution (not shown) as a fine stream 10 through a capillary nozzle 11 or spinneret located in a bath 12 of the latex. The coagulum 13 formed at the orifice is drawn awayfrom the nozzle 11 and out of the latex bath 12 at the same rate at which it is formed. This coagulum 13 is coherent and continuous but is intitially very weak so that it is .preferably supported by continuous belts 14 and the like .as soon as possible after it leaves the bath 12. The fila- .all of the electrolyte coagulant. Following washing the coagulum is dried by radiant heating means 17 or other techniques, fused, supercooled and finally stretched to produce orientation. The drying and fusing may be accomplished simultaneously or sequentially. As illustrated in Fig. 2 before drying, the dissimilar polymeric material 10 fills the inner area of the hollow fiber 13, after drying as shown in Fig. 3, the material 10 coats the inner surface of the hollow fiber 13. Following fusion, the fiber is fed through a non-solvent bath 18 at a relatively low temperature such as below the second order transitiontemperature to supercool the fiber after which it is wound around snubber rolls 19 or like means to stretch it as fully as possible without rupture to achieve orientation. Since the dissimilar polymeric material has a different orientability than the polymer from the latex, a fiber having a natural crimp is produced. The fibers so produced may be spun directly into yarns.

The hollow structure of the fibers presents the pos- ,sibilities for preparing light weight cold weather clothing that has excellent water repellency, abrasion resistance, and launderability.

By way of example a coagulant solution was prepared by dissolving 10 parts by weight of calcium chloride and 20 parts of zein in 40 parts of alcohol and 30 parts of water. That coagulant solution was forced through a 0.005 inch glass capillary into a bath of a latex containing 30 percent by weight of polymer solids of a polymer prepared from 97 percent by weight of vinylidene chloride and 3 percent of acrylonitrile. The coagulum formed at the capillary orifice was drawn out of the latex bath and water washed until substantially all of the calcium chloride was removed. The filamentary coagulum was dried at 100 C., fused at C., and led through a water bath at 25 C. to supercool it. The .fiber was then stretched to 4 times its original length and allowed to relax. The resulting fiber had a natural crimp and upon microscopic examination was found to consist of a hollow fiber having a hollow filamentary core.

By way of further illustration some of the same latex was forced through the capillary into a bath of the same coagulant, and after the washing, drying and fusing steps. a filamentary article was produced having a zein sheath over the crystalline polymer filament, capable of absorbing greater amounts of water than fibers prepared from the latex alone and which could be easily dyed with acid dyes.

We claim:

1. A process for preparing hollow fibers having a natural crimp from polymeric materials comprising as sequential steps the continuous contacting in fiber-forming relationship of a latex containing at least 25 percent by weight of polymeric solids of a normally crystalline vinylidene chloride polymer, with an aqueous coagulant solution comprising coagulative amounts of an electrolyte coagulant for said latex and fiber-forming amounts of a polymeric material dissimilar in orientation characteristics to'said polymer of said latex to form a coaxial filamentary coagulum having one polymeric material as a core and the other as a sheath, removing said filamentary coagulum from the point at which it is formed at the same rate at which it is formed, washing said filamentary coagulum to remove substantially all of said electrolyte coagulant, drying said filamentary coagulum at a rate and under conditions that any dispersant for said core polymeric is caused to diffuse through the polymer sheath to deposit a continuous coating of said core polymeric material on the inner surface of said polymer sheath, fusing said filamentary coagulum to form a continuous, hollow fiber, supercooling said fiber, and stretching said fiber beyond the elastic limit to produce orientation therein.

2. The process claimed in claim 1 wherein said elec- -trolyte coagulant is a water-soluble polyvalent metal salt.

3. The process claimed in claim 2 wherein said water- 'soluble polyvalent metal salt is present in said aqueous coagulant solution in a concentration of from 3 to 10 percent by weight.

6 References Cited in the file of this patent UNITED STATES PATENTS Snelling May 21, 1929 Alles June 13, 1944 Sisson et a1. May 4, 1948 Magat et a1. May 17, 1955 Boeuf Mar. 6, 1956 FOREIGN PATENTS Great Britain Sept. 10, 1931 

1. A PROCESS FOR PREPARING HOLLOW FIBERS HAVING A NATURAL CRIMP FROM POLYMERIC MATERIALS COMPRISING AS SEQUENTIAL STEPS THE CONTINUOUS CONTACTING IN FIBER-FORMING RELATIONSHIP OF A LATEX CONTAINING AT LEAST 25 PERCENT BY WEIGHT OF POLYMERIC SOLIDS OF A NORMALLY CRYSTALLINE VINYLIDENE CHLORIDE POLYMER, WITH AN AQUEOUS COAGULANT SOLUTION COMPRISING COAGULATIVE AMOUNTS OF AN ELECTROLYTE COAGULANT FOR SAID LATEX AND FIBER-FORMING AMOUNTS OF A POLYMERIC MATERIAL DISSIMILAR IN ORIENTATION CHARACTERISTICS TO SAID POLYMER OF SAID LATEX TO FORM A COAXIAL FILAMENTARY COAGULUM HAVING ONE POLYMERIC MATERIAL AS A CORE AND THE OTHER AS A SHEATH, REMOVING SAID FILAMENTARY COAGULUM FROM THE POINT AT WHICH IT IS FORMED AT THE SAME RATE AT WHICH IT IS FORMED, WASHING SAID FILAMENTARY COAGULUM TO REMOVE SUBSTANTIALLY ALL OF SAID ELECTROLYTE COAGULANT. DRYING SAID FILAMENTARY COAGULUM AT A RATE AND UNDER CONDITIONS THAT ANY DISPERSANT FOR SAID CORE POLYMERIC IS CAUSED TO DIFFUSE THROUGH THE PLOYMER SHEATH TO DEPOSIT A CONTINUOUS COATING OF SAID CORE POLYMERIC MATERIAL ON THE INNER SURFACE OF SAID POLYMER SHEATH FUSING SAID FILAMENTARY COAGULUM TO FORM A CONTINUOUSM HOLLOW FIBER, SUPERCOOLING SAID FIBER, AND STRECHING SAID FIBER BEYOND THE ELASTIC LIMIT TO PRODUCED ORENTATION THEREIN. 